Q&A

(2017) Question 8: What methods are you using to address alkylates’ sulfur contribution to the blend pool for Tier 3 compliance? Is your focus on feed pre-treatment or alkylate post-treatment?

For many, the alkylate’s sulfur contribution to the pool has not been the most economical sulfur to address when targeting Tier 3 compliance. STRATCO completed a survey of the sulfur content of alkylate streams in 2014; and that time, almost 90% of alkylate streams contained less than 10 ppmw of sulfur, with nearly 60% of those containing less than 5 ppmw of sulfur.

(2017) Question 9: What operating conditions in a catalytic polymerization unit are conducive to the formation of esters? What is the main effect that esters have on unit performance?

The mechanism by which oligomerization takes place over the SPA catalyst necessitates that a phosphate ester is formed between the catalyst and the olefin. The temperature required to dissociate the phosphate ester and convert the olefin depends on the olefin in question.

(2017) Question 10: What impact does silicon have on an isomerization catalyst? What are the symptoms that occur as evidence of a breakthrough?

When looking at chlorinated alumina-type catalyst, we have observed silicon will deposit on the catalyst in a similar fashion as other precious metal catalyst, distributing silicon throughout the pores and blocking access to active sites.

(2017) Question 11: In chlorided isomerization units, have you seen evidence of unconverted perchloroethylene (PERC) in the stabilizer bottoms stream?

Axens has evidence of the presence of organic chlorides in the isomerization stabilizer bottoms product. Since testing specifically for organic chlorides is not possible, one must compare the total chloride content of the isomerate against the HCl content to determine derived organic chloride content.

(2017) Question 12: Are you designing or revamping isomerization units’ radial reactor temperature indicators?

Honeywell UOP does not typically design Penex™ or Butamer™ units with radial temperature indicators in the reactors. UOP standard design is to have a single thermocouple at regular intervals in the catalyst bed. We typically show these TIs in a straight line down one side of the reactor.

(2017) Question 13: In chlorided isomerization units, what procedures are you using to shut down caustic-free and make the net gas scrubber safe for maintenance?

Some refiners want to steam out the scrubber to confirm that all caustic has been removed. This step is not necessary if the scrubber has been water-washed since caustic is soluble in water and there is no heavy hydrocarbon present in this vessel.

(2017) Question 14: For units that feed hydrocracked naphtha directly to the reforming unit, what is the typical concentration of sulfur in the feed? How does the concentration change over the hydrocracker catalyst cycle, and what are the impacts to the operation of the reformer?

At start-of-run conditions in a hydrocracking unit, the sulfur in hydrocracked naphtha can be between 2 and 5 ppmw. At end-of-run conditions, the sulfur can be between 10 and 20 ppmw. As high 40 ppmw has been observed at end-of-run conditions for one customer.

(2017) Question 15: For units that feed hydrocracked naphtha directly to the reforming unit, what is the typical concentration of olefins in the feed? How does the concentration change over the hydrocracker catalyst cycle, and what are the impacts to the operation of the reformer?

Olefins are expected to be saturated in the first bed of the hydrocracking unit. At start-of-run conditions, olefins are not expected to be found in hydrocracked naphtha.

(2017) Question 16: HCl concentration in the reformer net off-gas is being actively measured using hand-held detector tubes. Despite routinely measuring near-zero ppm (parts per million), chloride corrosion occurs downstream. What is the source of this corrosion, and what can be done to better measure and manage the source?

Organic chlorides can be invisible to simple HCl- detecting tubes. There are alternative measuring devices from which to choose to detect organic chlorides. It is well known that organic chlorides can be created from an alumina guard bed and cause green oil, chloride salt formation, and corrosion downstream.

(2017) Question 17: What is the importance of water content in reformer feed and recycle gas on the performance of the catalyst? What are your desired water concentrations in each of these streams?

Managing the water content in the reactive environment is critical for the overall performance of the reformer unit and catalyst. The content of water (H2O) must be controlled to allow for a sufficient quantity of hydroxyl [AlOH (aluminum hydroxide)] sites while simultaneously controlling the hydrogen chloride (HCl) levels to have the right balance of H2O/HCl to set the catalyst HCl content (Al-Cl).

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